Vacuum deposition apparatuses are widely used in the industry to deposit layers, sometimes very thin, of materials on substrates of various sizes.
It is known in the prior art that a valve-cell vacuum deposition apparatus includes:                at least one valve cell comprising:                    an outer enclosure,            an inner tank located inside the outer enclosure and adapted to contain a material to be evaporated,            an inner tank valve comprising a valve input port in fluidic communication with the inner tank and a valve output port,                        a vacuum deposition chamber,        a transfer tube comprising a tube input port connected to the valve output port and a tube output port located inside the vacuum deposition chamber, the tube output port including an injector adapted to generate a jet of vapour of the material to be evaporated inside the vacuum deposition chamber, the vacuum deposition chamber being connected to the outer enclosure by means of a connecting flange, and        pumping means adapted to evacuate the inside of the vacuum deposition chamber, the pumping means comprising a primary pump having a primary pump input and a primary pump output, and a secondary pump having a secondary pump input and a secondary pump output.        
The industry of microelectronics uses for example such a vacuum deposition apparatus to deposit materials using techniques such as Molecular Beam Epitaxy (MBE) or Molecular Beam Deposition (MBD). Conductive materials (copper, zinc, nickel, chromium, for example), isolative materials (oxides, nitride, for example), or semi-conductor materials (silicon, germanium, arsenic, phosphorus, antimony, gallium, indium, aluminium, for example) are deposited this way on substrate of silicon, germanium or other suitable materials.
The materials, either elemental or compound, and in particular semi-conductor materials, which are used in a very pure form in such vacuum deposition apparatuses, are stored in high-volume closed inner tanks for ensuring a continuous operation of these apparatuses during long periods and optimizing the costs of production of the semi-conductor components manufactured. The price of these materials being high, it is necessary to avoid the unnecessary loss or the irreversible degradation of all or part of the volumes stored in the inner tanks.
Therefore, the inner tanks of materials must be sealingly closed so as, for example, to prevent any leak of vapour of the material to be evaporated toward the outside of the inner tank or to prevent any oxidation or other chemical reaction with another compound (water, for example) entering into the inner tank. This makes it possible not to lose the content of the inner tank, which would cause additional costs of exploitation.
Likewise, the inner tank valve must be tight, that is to say that in its “closed” position, it totally blocks the flowing of the material to be evaporated between the inner tank and the vacuum deposition chamber. This makes it possible in particular not to pollute the vacuum deposition chamber with the material to be deposited when it is not desired, which would cause problems, for example when depositing another material on the substrate.
The vacuum deposition apparatuses according to the prior art do not make it possible to verify rapidly and in any circumstances the tightness of the inner tank or the inner tank valve, in particular in operation or during the use of pyrophoric compounds.
Leak detection systems are known from the prior art, which make it possible to test the tightness of the other members of the apparatus, such as the outer enclosure or the vacuum deposition chamber, for example.